Does a difference in educational level between spouses affect their relationship, and what is your advice in such a case?

If you are pleased with his proposal due to his religiosity and character, then accept him even if his educational level is lower, because religiosity and character are the most important qualities in spouses, and anything else is a secondary perfection. The Prophet, peace and blessings be upon him, said: "If there comes to you one whose religiosity and character you approve, then marry him."